6-1
Section
Introduction
80
6-1
Introduction
A message service is a command/response system used for data transmission
between nodes on a network, i.e., computer to computer, PC to computer, or
computer to PC. The message service can also be used to control operations,
such as mode changes. The message service is implemented by executing from
the user program the library functions for sending or receiving messages.
6-1-1 Message Service Specifications
Communications from an computer are executed according to the specifications
shown in the following table.
Item
Specifications
Direction of transmission
1:1
Message transmission or reception
1:N
Message transmission (broadcast)
Data length
2,012 bytes max. (including FINS header)
Data content
Any command/response data can be sent or received.
Depends on the message being sent.
6-1-2 Message Service Functions
FINS commands can be sent to specified nodes and FINS responses can be
received by executing C library functions from the user program to send and re-
ceive messages.
Functions
Features
Sending Messages
ClkSendFins library
function
(See note.)
This library function and driver call send command/response data.
Can be issued with respect to any Units at a PC, or to the Support Board or user
program at a computer.
Mainly used for sending FINS commands and responses. The FINS commands
and responses enable various types of control, and allow the status to be read.
Fixed-format data is prepared by the program and sent by executing clksend.
No special program is required at the receiving end if FINS commands and
responses supported by the receiving Unit are used.
When sending data to the computer with a user program, a program that can
process the received data is required.
When a response to a command is returned, a program for reading and analyzing
the response is required.
Receiving Messages
ClkRecvFins library
function
These library functions and driver call receive command/response data.
Data received by the Controller Link Support Board is read.
Mainly used for receiving FINS commands and responses. The FINS commands
and responses enable various types of control, and allow the status to be read.
Data is received by executing clkrecv, and it is analyzed by the program according
to a fixed format.
A program is required for analyzing the data that is received.
A program is required for preparing and sending responses when commands
requesting responses are received.
Note Using ClkSendFins or ClkRecvFins to send the “MEMORY AREA READ” and
“MEMORY AREA WRITE” FINS commands for PCs is equivalent to executing
the SEND and RECV ladder-diagram instructions.
